week 6

Question 1

types of reproductive systems

Answer 1

• asexual (no attraction
• isogamous sex (gametes of the same morphology)
• anisogamous (fusion of gametes)
• simultaneous hermaphrodite (has sex organs of both sexes)
• dioecious (reproductive system in two diff genders)
• facultative (combines sexual and asexual reproduction)
• in dioecious species, sex determination can be either genetic or environmental

Question 2

humans are:

Answer 2

• sexual
• anisogamous
• dioecious
• have genetic sex determination

Question 3

the two-fold cost of sex (AKA the cost of males)

Answer 3

Asexuality:
20 units of energy:
Asexual female - 100% of her genome
Anisogamous sex:
19.99 units of energy from sexual female, 0.01 units of energy from male: 50% of her genome
Isogamous sex:
10 units of energy from female 10 units of energy from male: 50% of her genome

Question 4

the two-fold cost of males

Answer 4

• other things being equal, asexual females will transmit their genome at twice the rate of sexual females because of anisogamy

Question 5

Why be anisogamous when it takes more energy for less of the genome

Answer 5

If you recombine it makes your offspring more different from each other than they would be under clonal reproduction - increased evolution
- males are often (not always) larger, more ornamented and more aggressive.

Question 6

The red queen hypothesis

Answer 6

A species must adapt and evolve not just for reproductive advantage but also for survival because competing organisms are also evolving.

Question 7

bateman’s principle

Answer 7

in most species, variability in reproductive success is greater in males than in females

• males invest in size for intrasexual competition
• males invest in ornaments for intrasexual signalling

Question 8

why should females pay any attention to male ornaments

Answer 8

• improves signalling quality
  The ‘sexy sons’ runaway
• slight bias for brighter males
• a female choosing a brighter males has sexier
• Genetic correlation between brightness and preference
• male brightness becomes greater
• payoff for choosing a bright male becomes greater

Question 9

What is the sexy son hypothesis

Answer 9

states that the females ideal mate choice is one whose genes will produce male with the best chance of reproductive success

Question 10

fisher principle

Answer 10

• suppose male births are less common than female
• a newborn male then has a better mating prospects than a newborn female, and therefore can expect to have more offspring
  (- parents genetically disposed to produce more males tend to have more than average numbers of grandchildren)
• therefore the genes for male-producing tendencies spread, and male births become more common
• as the 1:1 sex ratio is approached, the advantage associated with producing males dies away.